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3 years ago

13

How much force is needed to accelerate a 7.1 kg skier at 4 m/s/s?

2 answers:

zysi [14]3 years ago

5 0

Answer: 28.4

Explanation:

F=MA

F=(7.1)(4)

F= 28.4 N

liraira [26]3 years ago

4 0

You would need 28.4 N to accelerate

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. Two astronauts are 1.90 m apart in their spaceship. One speaks to the other. The conversation is transmitted to earth via elec

melomori [17]

Answer:

d= 1650 km.

Explanation:

Assuming that sound waves travel along a straight line at a constant speed of 346 m/s, we can find the time needed for the sound to travel the distance of 1.9 m between the astronauts, just applying the definition of average velocity, as follows:

$t = \frac{\Delta x}{v} =\frac{1.9m}{346m/s} = 5.5 msec (1)$

The electromagnetic waves travel in free space at the same speed of light in vacuum ( since light is a electromagnetic wave indeed), i.e., 3*10⁸ m/s.
Applying the same formula than in (1) we can solve for the distance d, as follows:

$d = v*t = 3e8 m/s*5.5e-3s = 1650 km (2)$

3 0

3 years ago

Usually, when the temperature is increased, what will happen to the rate of dissolving? A) It will stop. B) It will increase. C)

Montano1993 [528]

C) it will decrease

4 0

3 years ago

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How long does it take the sun to melt a block of ice at 0âc with a flat horizontal area 1.0 m2 and thickness 1.8 cm ? assume tha

snow_lady [41]

At least 20-30 seconds

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4 years ago

Gravitational potential energy depends on the ____________ of the object.

arlik [135]

Answer:

Height And Mass!

Explanation:

Got It from Google! I ain't smart XDD

4 0

3 years ago

A baseball of radius r = 5.2 cm is at room temperature T = 20.8 C. The baseball has emissivity of ε = 0.86 and the Stefan-Boltzm

Marrrta [24]

Answer:

$P = 12.37 \frac{J}{s} = 12.37 Watts$

Explanation:

Previous concepts

The Thermal radiation is one of "3 mechanisms who allows to bodies exchange energy".

The thermal radiation formula is given by:

$\frac{P}{A} = \epsilon \sigma T^4$

Where $\sigma = 5.67 x10^{-8} \frac{J}{sm^2 K^4}$

If we solve for P we got:

$P = A \epsilon \sigma T^4$

Since we have a baseball ball considered as a sphere the superficial area is given by:

$A = 4\pi r^2$

Solution to the problem

And if we replace this into our equation of P we got:

$P = (4\pi r^2) \epsilon \sigma T^4$

And we can reorder this like that:

$P = 4 \epsilon \pi \sigma r^2 T^4$

We can convert the radius to meters and we got:

$r= 5.2 cm*\frac{1m}{100 cm}=0.052 m$

Now we can convert the temperature to Kelvin and we got:

$T = 20.8 +273.15 = 293.95 K$

$\epsilon = 0.86$ the emissivity given

And now we can replace into the formula for P and we got:

$P = 4*0.86*\pi *(5.67x10^{-8} \frac{J}{s m^2 K^4}) (0.052m)^2 (293.95 K)^4$

$P = 12.37 \frac{J}{s} = 12.37 Watts$

6 0

3 years ago